Chemistry - GOC Question with Solution | TestHub

Negatively charged bases are far stronger than their neutral counterparts, so $\mathrm{P}{\mathrm{H}}_2^{-}$ and $\mathrm{O}{\mathrm{H}}^{-}$ beat $\mathrm{P}{\mathrm{H}}_3$ and ${\mathrm{H}}_2\mathrm{O}$. Within each pair, phosphorus is less electronegative than oxygen and holds the electron pair less tightly, making it more available : $\mathrm{P}{\mathrm{H}}_2^{-}$ $>$ $\mathrm{O}{\mathrm{H}}^{-}$ and $\mathrm{P}{\mathrm{H}}_3$ $>$ ${\mathrm{H}}_2\mathrm{O}$. Hence $\mathrm{P}{\mathrm{H}}_2^{-}$ $>$ $\mathrm{O}{\mathrm{H}}^{-}$ $>$ $\mathrm{P}{\mathrm{H}}_3$ $>$ ${\mathrm{H}}_2\mathrm{O}$.